public class Demo {
    public static void main(String[] args) {
        int a = 8;
        int b = a++;
        System.out.println(b);

        switch (a) {
            case 1:
                System.out.println(1);
                break;
            case 2:
                System.out.println(2);
                break;
            default:
                System.out.println("33svan");
                break;
        }
        //求阶乘1!+2!+3!+4!+5!
        int i = 1;
        int ret = 1;
        while(i <= 5) {
            ret = ret * i;
            i++;
        }
            System.out.println(ret);
        //数1到100的所有整数中出现多少个数字9
        int s = 1;
        int num = 0;
        for(s = 1; s <= 100; s++) {
            if(s % 10 == 9|| s / 10 == 9)
                num++;
        }
        System.out.println(num);
    }
}
